Modern architecture often utilizes contemporary designs incorporating non-right angles and coved or vaulted ceilings to provide an aesthetic appearance and environment. A coved ceiling is commonly defined as a ceiling formed in an arched manner at its junction with the side walls. Conventional construction methods generally require that arches or vaulted ceilings be constructed from flat wall board or panel surfaces arranged at non-right angles to the adjacent panels resulting in corners having angles greater than 90.degree..
During the construction of such homes or buildings, providing a coved finish to corners having non-right angles often proves troublesome and persons skilled in the art readily appreciate the great amount of skill required to achieve a smooth continuous finish to the dry wall compound applied to such corners. "Finishing operations" refers to the task of providing a smooth, continuous finish to the corner joint area after junction tape and plaster compound has been applied to secure the tape in the corner joint. Coved corners or joints may exist at the junction of two walls, at the junction of a side wall and a ceiling or possibly even at the junction of a side wall and a floor. The angles provided by these designs are greater than 90.degree. and normally are approximately 115.degree. to 120.degree..
Prior conventional tools have provided a poor solution to the problem of obtaining a smooth, continuous finish at coved corners. Conventional methods require a worker, after the corner joint has been taped, to apply plaster compound to an area adjacent the junction line of the corner (a junction line is the boundary between the two verging panel surfaces forming the corner joint) and along the outer edge of the junction tape, smooth the plaster compound over the edge of the tape and along one side of the junction line of the corner joint until a continuous smooth surface is achieved between the taped area and the adjacent panel surfaces, and then apply plaster compound to the opposite panel surface adjacent the junction line and repeat the smoothing process. Oftentimes, as the worker is attempting to smooth and feather the plaster compound on one panel surface near the junction line, an edge of his finishing tool contacts the dry plaster compound previously applied and smoothed on the opposite panel surface, thereby leaving a blemish or mark in the plaster compound requiring the worker to repair or "touch-up" that area, or causing small masses of the dry plaster compound to pull or break away from the dried plaster compound, such as in the form of chips or flakes, and mix with the wet plaster compound being applied to the opposite panel surface. The presence of the dry flakes in the wet plaster compound render providing a smooth finish thereto practically impossible. This can be a reoccurring nightmare for a worker as, while working on one panel surface, he must be sure not to contact the plaster compound applied to the opposing panel surface while still providing a continuous smooth surface between the taped area and the adjacent panel surface and along the junction line of the corner.
U.S. Pat. No. 3,878,581 provides a prior tool for finishing the taping applied over joints or panels of wall board wherein the tool is adapted to conform to irregularities in the wall board construction. The tool comprises the combination of an elastomeric blade having a lining on its operative face for protection against abrasion and being cushioned against a rigid back. The elastomeric blade has a protruding part with an edge or edges parallel with the corresponding edge or edges of the rigid back member. The protruding part or extension of the elastomeric blade that is cushioned when in use provides flexibility while applying plaster compound in the finishing operation. The flexibility provided by the extension only occurs in a direction transverse to the edge of the extension or of the rigid back member and, hence, the angle of the corner for which the tool may be used is fixed by the limited flexing capability of the tool.
An alternative embodiment of the prior tool presents a double-edge corner structure capable of finishing both sides of the corner tape in one stroke. In use, this embodiment of the prior tool and its shape-conforming protruding portions yield when pressed upon the wall board surface. The fixed angle provided in the tool, which is intended to conform to the angle of the corner to be smoothed, dictates that the tool be positioned substantially transversely to the wall board surfaces while being moved therealong to provide continuous contact between the entire length of the protruding edges and the taped area and adjacent wall board surfaces. This requirement detracts from the efficiency required for such a finishing tool and renders the use of the tool impractical. Moreover, the fixed angle in which the tool is formed also dictates that the tool be used only with angles corresponding to the angle of the double-edge tool.
Another prior wall corner finishing tool is presented in U.S. Pat. No. 4,619,013 which describes a hand finishing tool for dry wall board installation consisting of a main body formed in two substantially flat sides extending radially from a common line, a manual tool gripping means pinned to the inner surface of the main body, and a tool biasing means to outwardly bias the flat sides of the main body to temporarily enlarge the angle of the tool during use. The flat sides of the main body diverge from a common line to define a dihedral configuration, preferably at a uniformly set angle, which is greater than 90.degree.. The tool biasing means is adapted to enlarge the angle formed by the flat sides juxtaposed to one another that the sides normally define during tool use so as to aid in gaining the smooth surface effect of the ceiling material being deposited into the wall board corners. The use of this prior tool is limited to corners having an angle of 90.degree..
Prior attempts to provide a finishing tool which will distribute and blend the wet plaster compound and provide a smooth continuous finished surface to the taped area and the adjacent wall board surfaces in corner joints having an angle greater than 90.degree. have been unsuccessful. Such prior tools have been mostly rigid and have lacked the flexibility and shape-conforming features to provide a smooth, continuous finished surface to a variety of angles with a minimum of strokes or passes of the tool.